Self-normalized photoacoustic techniques for thermal diffusivity measurements in metals

The analytical solution for the one-dimensional heat diffusion problem involving an harmonic heat source in a single layer, in the surface absorption limit, is used to provide self-normalized methodologies for thermal diffusivity measurements in metals, by using the photoacoustic technique. The self-normalized procedure involves the photoacoustic phase lag between the rear and front configurations. Three methodologies are described. Two of them involving linear fits in the photoacoustic thermally thin and thermally thick regimes. Comparison between the theoretical normalized equations and the corresponding normalized experimental data allows for the development of criteria on the selection of an appropriate modulation frequency range where a reliable analysis can be done. Computer simulations and thermal diffusivity values measured for some materials are also provided. The values of thermal diffusivity for each material, obtained by using the different reported methodologies, were found to be close to each other, showing self-consistency between the different methodologies described in this paper.